The proposed research is directed at establishing the structure of the Type I and type II chicken collagen genes, and at least one of the type V chicken collagen genes and at gaining some insight into the way they are selectively expressed in some tissues and totally repressed in others. Having already isolated the entire 38kb proAlpha2(I) collagen gene, and part of the proAlpha1(I) collagen gene, we plan to first construct a chicken-lambda library. We will then use it to isolate the 5 feet and 3 feet coding and flanking gene regions of the Alpha1(I), Alpha1(II) and a type V gene, on the assumption that control elements are most probably located here. The DNA sequence of this region will be determined, and specific restriction fragments from these regions will be used to determine if there are changes in chromatin structure (DNAse I hypersensitive sites) prior to expression and to explore the possibility that DNA segments can and/or do undergo conformational changes from the right-handed B form to other conformations such as cruciform structures or the left handed Z form. Embryonic chick chondrocytes and myoblast cell cultures will be used as model systems for studying changes that accompany dedifferentiation (in chondrocytes) and sequential expression of type V, III and then I collagen (in myoblasts).